Having A Baby Alters A Man’s Brain, Study Says

When you become a father, you undergo something of an unstoppable transition — and not just in your outlook. First, your testosterone levels drop, production of nurturing hormones like prolactin and oxytocin increases, and as a product of this most new dads gain weight. But changes to your brain — reflected in a change in focus, memory, and emotions, as if your brain has flipped a switch — usually get overlooked. But a new study confirms that it’s not all in your head. “Dad brain” is real and it’s impact is fundamental.

The new study, published in the journal Cerebral Cortex, reveals that a man’s brain undergoes a slight shrinkage when his newborn arrives, complementing similar research showing that women undergo cerebral changes during motherhood too.

“Across the board, we found similar reductions in gray matter, sort of suggesting that the brain was becoming more streamlined and possibly more efficient over that transition to first-time parenthood in the fathers,” says Darby Saxbe, Ph.D., a professor of psychology at the University of Southern California and one of the lead researchers on this study.

The brain is characterized by something scientists call neuroplasticity, or the ability to adapt to thrive in new situations and learn new skills by creating new connections between neural pathways. The brain is dynamic and rewires when it needs to incorporate new ways of functioning that it didn’t previously — like having a baby.

Going into this research, the scientists wondered whether there would be plasticity changes in the “parental caregiving brain network,” areas of the brain that prior research has shown to be involved in taking care of a child. These mainly include the cortical areas, such as the networks responsible for emotion regulation and empathy, as well as the subcortical areas, which are more related to primary instincts like arousal, vigilance, motivation, and reward.

For the study, Saxbe’s team pored over data on the brains of 57 men, averaging in their mid-thirties: 20 dads-to-be from the U.S., 20 from Spain, and 17 childless men from Spain. In Spain, the participants had their brains scanned before their partners got pregnant, and then two to three months after they had given birth. In the U.S., the fathers’ brains were examined 30 weeks into their partner’s pregnancy, and then between seven and nine months after the baby was born.

Although the men who did not have a baby during the time of the study had no variations in their brain structure, changes were evident for the new fathers. “In both samples of fathers, we found that there was volume reduction in the cortical area of the brain,” Saxbe says.

Specifically, the shrinking was prevalent in areas of the brain that are active when we’re at rest and daydreaming, not focusing on a task. “When the brain is not involved in a task, like sorting numbers, we daydream and we often think about other people,” says Saxbe. “Those are the regions that lost some volume in this study.”

The slight shrinkage in this area can be attributed to the brain trimming back superfluous neuronal connections, streamlining its pathways, and therefore losing mass. This is all so it can become more efficient in processing social information. It’s like getting tunnel vision as an adaptive behavior to take care of your children.

Saxbe says this makes sense as adaptive behavior. Communicating and empathizing with a nonverbal infant and understanding their intentions is a skill people don’t tend to have until they need to. It would reasonably follow that the brain undergoes some significant changes in order to do so, including getting rid of the extra noise in the brain.

“Much like at other critical windows in the lifespan, when we consolidate and prune, the brain becomes more streamlined or more efficient,” says Saxbe. It’s similar to what happens in a child’s infancy; the brain slightly shrinks to hone in on the learning skills necessary for growing, and pathways become more defined.

These findings in new dads are in line with what happens in the brains of new moms. However, new moms also experience changes in their subcortical areas — parts of the brain more related to instinct, emotion, fear, and perception of threat — according to seminal research in the field. “That might have to do with the fact that the mothers experienced pregnancy and the fathers didn't,” Saxbe says.

As the new study is preliminary, more research is needed to pinpoint exactly what’s happening in new dads’ brains.

“Fathers tend to get neglected in the research and also when it comes to policy,” Saxbe says. “So I'm hoping that work like this can shed light on this idea that men really are important parents in their own right, and that's reflected in their neurobiology.”